Wirkungen organischer Substanzen auf Boden- und Düngerphosphat Teil 1: Einfluß von Stroh- und Maiswurzelextrakten auf die Löslichkeit von Boden-und Dünger-P

Effects of organic substances on soil- and fertilizer phosphate Part 1: Influence of straw or maize-root extracts on the solubility of soil and fertilizer P The effects of straw and maize-root extracts on the solubility of soil and fertilizer phosphate were tested in incubation trials. The following results were obtained. 1. Addition of an extract of unrotted straw (10 g straw/100 g soil) to incubate a brown-earth soil, (high or low in P) for 1–14 days did not have any significant effects on the H₂O and CAL P-fraction as compared to a KH₂PO₄ control, but markedly increased transformation of ‘easily soluble’Fe- and Al-phosphates (?15 to ?40 ppm) into ‘less soluble’forms (+15 to +20 ppm). Addition of an extract of rotted straw decreased the amounts of water extractable P and ‘easily soluble’Fe- and Al-phosphates but CAL-extractable P and ‘less soluble’Fe- and Al-phosphates were increased. 2. Incubation of the same soil (P-enriched) with an extract of maize roots (roots: soil = 1:3) for 1 day resulted in a reduction in the fixation of fertilizer phosphate (34 as compared to 42%) and in a decrease of fertilizer P recovered as ‘less soluble’Fe- and Al-P (from 31 to 11%); however, fixation was markedly increased after 14 days.